There may be no single cause of bipolar disorder (aka manic depression). Instead, research indicates the causes of bipolar disorder are probably a combination of biochemical, genetic and environmental factors that may trigger and perpetuate the chemical imbalances in the brain.
Net worth: $829 million. Telecommunications mogul Strive Masiyiwa is widely regarded as the richest man in Zimbabwe and is one of the richest men in Africa with a net worth of more than US$800 million.
The Black Billionaires 2015. Of the 1,826 people who made it to the 2015 FORBES list of the Worldâs Billionaires, 11 of them are black, up from 9 a year ago. Nigerian cement tycoon Aliko Dangote is still the richest black person in the world, with a fortune estimated at $15.7 billion. He is followed by Saudi-Ethiopian construction magnate Mohammed Al-Amoudi, who is worth $10.8 billion. This year, two new moguls join the ranks of the richest black people on earth.